"We have had very good people that had very good ideas and no one predicted that we would even be in the hunt,” Carson said Sunday on ABC's "This Week." "It really is quite spectacular what we were able to do. But the fact of the matter is now we’re in a different ballgame and we need the ability to execute and not just have good ideas."

The comments came after three of his top aides -- including campaign manager Barry Bennett and communications director Doug Watts -- announced Thursday they were resigning from the campaign. Deputy campaign manager and policy director Lisa Coen has also resigned, according to Carson's new campaign manager, Ed Brookover.

Carson said he had plans to make “very substantial changes,” which Bennett did not agree with.

“I was going to make some very substantial changes and Mr. Bennett decided that he could not live with those changes and that’s OK,” Carson said. “It doesn’t diminish anything that he’s done. I think he’s done a fantastic job.”

Bennett and Watts both said Carson’s business manager Armstrong Williams was “the factor” of the staff shakeup. Though not officially associated with the campaign, Williams is one of Carson’s closest advisers and has been with him long before he launched his presidential bid.

Throughout Carson’s campaign, conflicting messages have come from Armstrong and Carson's staffers, who previously acknowledged that Williams created a problem. Bennett told ABC News last month the relationship with Armstrong was “a disaster.”

Carson acknowledged that Williams had made some “bad judgements.”

"He’s made some bad judgments. There’s no question about it,” Carson said. "But, you know, he’s a friend. I think he’s a valuable individual.”

"We can’t have people working at cross purposes, and that’s one of the things that has to be fixed and is being fixed and is fixed, in fact, at this point," he added.